Previous judges have found the collection program constitutional, unlike Monday's ruling

The U.S. Department of Justice defended the National Security Agency's massive phone records collection program after a U.S. District Court judge ruled Monday that the program is likely to violate the U.S. Constitution.

Judge Richard Leon of the U.S. District Court for the District of Columbia ruled that the NSA's controversial collection of U.S. telephone records may violate the Fourth Amendment's protection against unreasonable searches and seizures. Four plaintiffs asked the judge to order their records removed from the NSA's database, and the judge agreed, but stayed his ruling pending a DOJ appeal.

The DOJ has "seen the opinion and are studying it," Andrew Ames, spokesman for the DOJ's National Security Division, said in an email. "We believe the program is constitutional as previous judges have found. We have no further comment at this time."

The NSA referred questions to the DOJ.

Fifteen judges in the U.S. Foreign Intelligence Surveillance Court have approved the program on 35 separate occasions. Leon's ruling, if it stands, may set up a Supreme Court case to arbitrate between Leon's decision and the FISA court, said Ross Schulman, public policy and regulatory counsel at the Computer and Communications Industry Association, a tech trade group that's been critical of the NSA program.

"It is encouraging to see the judiciary taking up the important questions of metadata analysis and realizing the great insights about one's life that can be gleaned from such large sets of information," Schulman said by email. "While this kind of large-scale data crunching can lead to great advances in medicine, transportation, and even simply movie rentals, it raises serious concerns when governments do it to pick out the relationships between its citizens."

Other critics of the NSA program cheered Leon's ruling.

"This is a strongly worded and carefully reasoned decision that ultimately concludes, absolutely correctly, that the NSA's call-tracking program can't be squared with the Constitution," American Civil Liberties Union deputy legal director Jameel Jaffer said in a statement.

The NSA's defense of the program is partly based on a 1979 U.S. Supreme Court case in which the court ruled that an individual suspect's Fourth Amendment rights weren't violated with a wiretap.

"The idea that this narrow precedent authorizes the government to place every American under permanent surveillance is preposterous," Jaffer said. "We hope that Judge Leon's thoughtful ruling will inform the larger conversation about the proper scope of government surveillance powers, especially the debate in Congress about the reforms necessary to bring the NSA's surveillance activities back in line with the Constitution."

The Smith v. Maryland case from 1979 covered a "few days" of phone records from one person, added Greg Nojeim, the director of the freedom, security and technology program at the Center for Democracy and Technology.

"The court's ruling means that the NSA's bulk collection program is skating on thin constitutional ice," he said by email. "Judge Leon clearly rejected the government's claims that the program is an effective anti-terrorism tool."

The ruling could bolster efforts in the U.S. Congress to limit the NSA program, Nojeim added.

Grant Gross covers technology and telecom policy in the U.S. government for The IDG News Service. Follow Grant on Twitter at GrantGross. Grant's email address is grant_gross@idg.com.